Intramembranous bone formation after callus distraction is augmented by increasing axial compressive strain

Area of Science:

• Orthopedics
• Biomaterials Science
• Regenerative Medicine

Background:

• Mechanical forces critically influence distraction osteogenesis outcomes.
• Interfragmentary movements, including shear and bending, affect callus formation and healing.
• Previous studies linked instability and cartilage presence to delayed bone healing.

Purpose of the Study:

• To investigate the effects of purely axial compression on bone ossification during callus maturation.
• To differentiate the impact of movement direction on bone regeneration.
• To evaluate small (0.1 mm) versus moderate (0.6 mm) axial compression in a sheep model.

Main Methods:

• A novel lateral callus distraction model was used in sheep tibias.
• Electromechanically controlled axial cyclic compression was applied to the regenerate.
• Micro-computed tomography (μCT), histology, and immunohistochemistry analyzed tissue regenerates.

Main Results:

• Moderate axial compression (0.6 mm) significantly increased bone formation compared to small compression (0.1 mm).
• Key bone formation metrics like fractional bone volume, trabecular thickness, and mean spicule height were significantly enhanced.
• No endochondral ossification was observed, suggesting a shift towards intramembranous ossification.

Conclusions:

• Moderate axial interfragmentary movement augments intramembranous ossification in distraction osteogenesis.
• Eliminating shear strain and maintaining neovascularization are vital for optimal bone regeneration.
• Clinical applications should focus on moderate axial movement with minimized shear strain for enhanced healing.